Paint sprayers, wherein the paint is contained in a first container and the propellant gas is contained in a second container, have advantages over single aerosol cans having both the propellant and paint contained therein. The latter form of packaging requires extensive inventories of aerosol cans with various colors, and the sales of a given color of paint may not be sufficient to warrant the production, marketing and stocking of aerosol cans with that given color of paint. The same may be said for other types of products marketed in aerosol cans, for example different types of insecticides, etc. However, in a two-container, hand-held spraying system of the aforementioned type, the product container may be used interchangeably with different colors or types of paints since the product container is detachable from the remainder of the spraying system. After spraying a particular color or type of paint placed in the product container, the product container is detached and cleaned so as to be ready to be refilled with a different (or the same) color or type of paint to be next sprayed. The propellant container is likewise detachable from the spraying system, so that when the propellant has been used up in the propellant container, a new container filled with propellant may be attached to the spraying system. As can be seen, such systems have considerable versatility and have become popular.
One type of two container system commercially available utilizes two side-by-side containers connected together by a bridge member. Propellant from the propellant can flows through the bridge and out the bridge through a nozzle that overlies a product tube extending down into the product container. The fast flow of the propellant over the end of the product tube creates a lowered pressure at that point such that the air pressure acting on the liquid in the product container forces product up the product tube and into the stream of propellant gas. In such systems a very low product to propellant ratio is obtained for reasons including that the pressure is only moderately lowered over the top of the product tube. Modifications of this type of side-by-side system have the bridge with its exit nozzle positioned forward of the top of the product tube, and with a form of nozzle insert positioned in the bridge near the exit nozzle. The propellant gas passes through the nozzle insert and likewise acts to lower the pressure over the end of the product tube to cause product flow into the stream of propellant gas. Such a latter system with a nozzle insert has a better product to propellant ratio, for example, of the approximate order of three to one, but there is still an excessive use of propellant. The nozzle inserts of such systems generally are poorly designed and do not create a sufficient vacuum over the top of the product tube.
A further type of two container system has the propellant container mounted piggyback on top of the product container. Product from a tube in the bottom container can flow up through a tube in the propellant container to an actuating button on the top of the propellant container. A nozzle insert in the button, generally operational as previously set forth, has resulted in the obtaining of enhanced product to propellant ratios of five or six to one for products of the viscosity of water. Such systems would benefit from a still further enhanced product to propellant ratio.